A light emitting diode (LED) includes a P-N junction diode having a characteristic of converting electric energy into light energy, and may be formed by using compound semiconductors of group III-V elements on the Periodic Table. In addition, the LED may represent various colors realized by adjusting the compositional ratio of the compound semiconductors
When forward voltage is applied to the LED, electrons of an N layer are combined with holes of a P layer, so that energy corresponding to an energy bandgap between a conduction band and a valance band may be generated. In the case of the light-emitting device, the energy is generated in the form of light.
A nitride semiconductor represents excellent thermal stability and wide bandgap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. Specifically, blue LEDs, green LEDs, ultra-violet (UV) LEDs using nitride semiconductors are commercialized and widely used.
The LED emits light through the recombination of electrons produced in an N type structure and holes produced in a P type structure.
Meanwhile, since electrons have masses and mobility greater than those of holes, the electrons are prevented from being overflown by using an electron blocking layer including a material, such as P type AlGaN, representing a high potential barrier. However, as the stress occurs due to the lattice mismatch between a barrier of an active layer and the electron blocking layer, the energy band is bent. Accordingly, the injection efficiency of the hole is degraded, so that the light emitting efficiency may be degraded.